Mucolipidosis Type I (ML I or Sialidosis)

What is mucolipidosis type I (sialidosis)?

Sialidosis is the first type of mucolipidosis, which is a group of metabolic disorders that affect the body’s ability to perform normal processes that involve the turnover of materials within cells. It is an inherited disorder that often affects numerous organs and tissues, as well as the nervous system.

Sialidosis is divided into two subtypes: type I (also referred to as cherry-red spot myoclonus syndrome), and type II, which is further divided into congenital (present at birth) and infantile forms. Type II is much more severe than type I.

Sialidosis affects males and females equally. The exact prevalence of the disease is unknown.

What are the symptoms of mucolipidosis type I (sialidosis)?

It is important to note that each patient may not have every symptom listed below.

Sialidosis type I:

Symptoms for type I usually develop during patients’ teens or twenties.

Problems walking
Red spots in eyes
Impaired vision
Involuntary muscle contractions
Lack of coordination
Tremors
Seizures
Over time, difficulty standing, walking, and/or sitting

Sialidosis type II:

Sialidosis type II symptoms are usually present at birth or develop by the time the infant turns one.

Excessive swelling throughout the body at the time of birth
Coarse facial features: puffy eyelids, enlarged gums, flat nasal bridge, abnormally large tongue, high forehead
Enlarged liver and/or spleen
Skeletal malformations
Dislocated hips
Involuntary muscle contractions
Lack of coordination
Extreme swelling in the abdomen
Low muscle tone
Impaired intellect that either starts as or becomes severe
Failure to thrive
Recurring respiratory infections
Seizures
Short stature
Red spots in eyes
Impaired vision
Hearing loss

What causes mucolipidosis type I (sialidosis)?

Sialidosis happens because of a mutation that causes a deficiency in an enzyme called neuraminidase (sometimes called sialidase). This enzyme breaks down certain proteins, which help the cell function properly. The deficiency in neuraminidase leads to an accumulation of the proteins in neurons, bone marrow, and other cells that defend against infection. Too much of these materials makes them toxic, which leads to symptoms.

To learn more about how the mucolipidoses are caused and inherited, click here.

How is mucolipidosis type I (sialidosis) diagnosed?

Sialidosis is diagnosed using the following procedures:

Thorough medical history
Findings of characteristic symptoms
Thorough clinical evaluation
Urine test
Blood tests
Skin biopsy
Prenatal (before birth) diagnosis via amniocentesis and chorionic villus sampling

What are the treatments for mucolipidosis type I (sialidosis)?

Sialidosis treatment caters to the symptoms of each individual patient. It includes:

Anti-seizure medications
Genetic counseling
Other symptomatic treatments

Where can I find out more about sialidosis?